The white dwarf is an extinct star of the same size as our own planet. The discovery has been made with the Hubble telescope's ultraviolet light, with a regular optical telescope the white dwarf would have looked normal.
Researchers believe that the white dwarf's strong gravity pulled in a dwarf planet or a large icy object from the system's own version of the Kuiper belt – the ring of frozen celestial bodies that in our solar system lies beyond Neptune.
When the object was torn apart, the analysis revealed that it consisted of two-thirds water ice and contained unusually much nitrogen, along with sulfur, carbon, and oxygen. Such material is usually thrown out long before a star becomes a white dwarf, which makes the discovery surprising.
The phenomenon also gives a glimpse of our own future. In a few billion years, the sun will become a white dwarf. Then its gravity can pull in and tear apart objects from our own Kuiper belt – just like in the current solar system.
The researchers now hope to be able to use the James Webb telescope to see even more details, such as water vapor and other molecules, in infrared light.
